1. Field of the Invention
The present invention relates to a fuel injection valve for an engine.
2. Description of the Related Art
A technique for promoting the atomization of the fuel injected from the fuel injection valve is disclosed in Japanese Unexamined Patent Publication No. 9-32695. This patent publication contains a description to the effect that the fuel flows along the inner wall surface of the fuel injection valve into the nozzle holes of the fuel injection valve. When flowing into the nozzle holes, therefore, the fuel is separated from the inner wall surface of the fuel injection valve. The fuel that has flowed into the nozzle holes is whirled periodically, and the fuel injected from the nozzle holes develops a self-excited vibration, with the result that the atomization of the fuel injected from the fuel injection valve is promoted.
As long as the atomization of the fuel injected from the fuel injection valve is promoted, however, the distance that can be covered by the fuel injected from the fuel injection valve is generally reduced (i.e. what may be called the penetrating force of the injected fuel is reduced). Specifically, with the fuel injection valve described in Japanese Unexamined Patent Publication No. 9-32695, the atomization of the fuel is promoted to such an extent that the penetrating force of the injected fuel is reduced. In an internal combustion engine (hereinafter referred to as the “engine”) so configured that the fuel is injected directly into the combustion chamber from the fuel injection valve, the air flows violently in the combustion chamber in the case where the load on the engine is large. In such a case, a small penetrating force of the injected fuel could fail to disperse the injected fuel sufficiently in the combustion chamber. This is an undesirable phenomenon hampering satisfactory fuel combustion. The engine having the fuel injection valve disclosed in this conventional technique, therefore, cannot sufficiently meet the requirement to burn the fuel satisfactorily when a large load is placed on the engine. This is not limited to the case when a large load is placed on the engine, but generally applies to a case in which a large penetrating force of the injected fuel is required to assure satisfactory combustion of the fuel.
Accordingly, the object of this invention is to provide a fuel injection valve for assuring satisfactory combustion of the fuel or, in particular, to a fuel injection valve which can burn the fuel satisfactorily as possible by promoting the atomization or increasing the penetrating force of the injected fuel, as required.